The present invention relates to an insulating covering, in particular a floor covering, for acoustic insulation of car body parts according to the precharacterising clause of claim 1.
Acoustically effective insulating coverings are used in vehicle construction, in particular in tractors and other commercial vehicles, in which floor panels, loading areas, luggage boots etc. are provided with insulating coverings, to reduce the level of noise emitted by these car body parts. Measures for reducing the noise emitted into the inside of the vehicle are of particular importance, since noise is known to cause subjective feelings of ill health, for example headaches, a pounding heart or elevated blood pressure. It is therefore the desire of the modern vehicle industry to reduce as far as possible the noise level in vehicles.
The known measures for reducing the noise level produced by vibration car body parts are currently limited substantially to two measures:
a) rigidification and vibration damping of the car body parts in question by adhered or fused-on, bending resistant dissipatively acting damping layers;
b) covering of the damped or bare car body parts with a so-called spring-mass system, i.e. a covering of porous resilient material (nonwoven or foam) with a heavy backing layer applied thereto. Such coverings are often provided inside the vehicle with a decorative or carpet layer.
In general, the spring layer consists of porous materials having the lowest possible modulus of elasticity and a filled PU foam is used for the mass layer or heavy backing layer. These acoustically insulating coverings consist of two or more layers of different materials, which makes the production and recycling of these coverings more difficult and expensive.
These insulating coverings are generally heat- and damp-sensitive, are not very robust and are not really suitable for use in open vehicles, for example agricultural vehicles, or in construction machines. Moreover, in the vehicle industry tight limits are set in relation to the amount of space which may be used in total for the insulating system and to the additional weight associated therewith.
It is therefore the object of the present invention to provide an acoustically insulating covering which does not exhibit the disadvantages of the known acoustic insulation systems.
In particular, it is the object of the present invention to provide an insulating covering which may be made of a single material and in a single forming process, so as to achieve lower cost manufacture than conventional acoustic insulation systems allow.
According to the invention, this object is achieved by an insulating covering having the features of claim 1. In particular, the nub of the invention is that the insulating covering comprises three different functional zones: a first zone (A) comprises a top layer which lends stability and non-crushability to the entire component and serves as mass layer for the spring-mass system according to the invention; a second zone (B) consisting of a plurality of open cells, the cell walls and enclosed air of which assume the function of a resilient spring for the spring-mass system; a third zone (C), which separates the second zone (B) and the cellular layer thereof by means of small spacer elements from a car body part to be insulated. The cross-sectional area of each of these spacer elements is substantially smaller than the cross-sectional area of the cell walls forming the cells. It goes without saying that the top layer may be provided on the upper side with a pattern and is made of abrasion-resistant material.
The present invention is additionally based on the knowledge that the sound-absorbing and sound-insulating action within the insulating covering may be improved substantially if the air flow in the zone (C), i.e. between the vibrating car body part and the cellular layer, undergoes frictional loss. To this end, only the smallest possible supporting elements are arranged in the third zone, hereinafter also known as the spacing zone, the cross-sectional area of said supporting elements being substantially smaller than the cross-sectional area of the cell walls. Thus, controllable lateral air flow resistance is produced in the third zone, which results in additional energy dissipation. The sound emission, here under consideration, in motor vehicles, railway vehicles or machines is produced by bending vibrations of the car body panels. When the car body parts vibrate, localised excess pressure is produced in the air above the upwardly vibrating areas thereof, while a partial vacuum is produced above the adjacent downwardly vibrating areas. Owing to the lateral air flow in the third zone, made possible by the invention, partial pressure equalisation is achieved between the areas of excess pressure and partial vacuum. This means that less pressure is built up in the air column above the upwardly vibrating areas and reduced acceleration is produced in the first zone of the insulating covering. The same also applies to the downwardly vibrating car body areas.
Further particularly advantageous developments of the insulating covering according to the invention are distinguished by the features of the subclaims.
In particular, a preferred embodiment of the cellular layer of the insulating covering comprises a plurality of cells with a square base of approximately 42xc3x9742 mm2. In a further preferred embodiment, the spacer elements are arranged at the points of intersection of the cell walls and comprise a cross-sectional area of up to 5 mm2 and a height of from 1 to 4 mm. The cell walls are of rubber or PU and exhibit a thickness of 2 mm and a height of up to 18 mm.
In a particular embodiment, at least one part of the cell walls between adjacent spacer elements comprises at least one recess. Thus, the lateral air flow resistance may be simply regulated or optimised. In a preferred embodiment, these recesses comprise a height (Bxe2x80x2) of up to 4 mm. The ratio of the width (D) of these recesses to the distance (E) between adjacent spacer elements is ratio 3:4.
In a particularly advantageous embodiment, all the zones, and in particular the entire insulating covering, are made of a single material and the desired physical properties are achieved by suitable shaping or dimensioning of the individual zones. In particular, the individual zones may exhibit different densities. Thus, the insulating covering according to the invention is distinguished not only by its good acoustic properties, its robustness and ease of recycling, but also by a particular cost-effective method of manufacture.
Thus, according to the invention, a weather-resistant insulating covering is provided which exhibits easily optimisable acoustic efficiency, in particular in the frequency ranges which are particularly disturbing in open vehicles, in relation to known acoustic insulation systems.
These properties may be achieved without the need for additional layers.
Many other embodiments lie within the normal technical competence of a person skilled in the art and will be obvious to the person skilled in the art from the teaching disclosed without the need for an inventive step.